Studies on the mechanism of serotypic transformation in Paramecium aurelia: II. The effects of actinomycin D, puromycin, and chloramphenicol on transformations induced by patulin, acetamide, and antiserum

Abstract

The effects of actinomycin D, puromycin, and chloramphenicol on four more induced antigenic transformations in Paramecium aurelia, all in stock 51, syngen 4, have been studied: that of D to B induced by patulin, those of D and of B to E induced by acetamide, and that of B to D induced by homologous antiserum. The results of these experiments extend and confirm those reported in our first study on the effects of the same antibiotics on the antiserum-induced transformation of serotype D to B. All these induced transformations can be both inhibited and stimulated by the antibiotics. In general, simultaneous treatment with high concentrations of both antibiotics and inducers gives an inhibition of transformation. As the concentrations of both inducer and antibiotic are reduced, or as the concentrations of the antibiotics alone are reduced, points are reached where further reduction stimulates the transformation. Furthermore, stimulation of transformation has been obtained from a combination of a high concentration of actinomycin D and a low concentration of patulin, thus confirming results obtained when a high concentration of actinomycin D and a low concentration of homologous antiserum were previously used in the transformation of D to B. Finally, the same low concentration of an antibiotic may inhibit the transformation if added after the inducer, yet increase the percentages transformed in a given time if added before the inducer. The data give strength to (1) the view that transformation from one serotype to another involves repression or a gene for one antigen and derepression of a gene for a different antigen; or, at the level of protein synthesis, cessation of synthesis of one antigenic protein followed by synthesis of a different protein; and (2) the hypothesis that when the antibiotics, actinomycin D, puromycin, and chloramphenicol inhibit or accelerate transformation, they are working essentially in the same way, i.e., by inhibiting a synthesis, that of the induced antigen in inhibition, that of the pre-transformation antigen in acceleration.